Conventionally, what has been known is an antenna device having only a limited space as in the case of an antenna device for vehicle that is equipped with an antenna case. FIGS. 41 to 43 show the configuration of the conventional antenna device 100. FIG. 41 is a side view showing the configuration of the conventional antenna device 100. FIG. 42 is a side view showing the internal configuration of the conventional antenna device 100. FIG. 43 is an exploded view of the conventional antenna device 100.
The conventional antenna device 100 shown in the above diagrams is an antenna device that is attached to a roof of the vehicle. When being attached to the vehicle, a portion protruding from the vehicle is about 66 mm in height, about 63 mm in width, and about 153 mm in length. The antenna device 100 takes a low-profile, and is able to receive AM broadcasting and FM broadcasting. The antenna device 100 has a streamline shape in such a way as to taper toward a tip. A flexible base pad that is made of rubber or elastomer is fitted on a lower surface of the antenna device 100, making it possible to attach the antenna device 100 to the vehicle in a watertight manner.
The conventional antenna device 100 includes an antenna case 110 which is made of resin; a metallic antenna base 120 on which a lower portion of the antenna case 110 is fitted; an antenna substrate 130 which is attached perpendicular to the antenna base 120; an amplifier substrate 134 which is attached parallel to the antenna base 120; a top section 131 which is formed into a mountain shape in cross section and is so disposed as to straddle the antenna substrate 130; and a GPS antenna 132 which is attached onto the antenna base 120. The antenna case 110 is made of synthetic resin that allows radio waves to pass therethrough, and includes an outer shell section 110a which has a streamline outer shape in such a way as to taper toward a tip. In the antenna case 110, a space that houses the upright installed antenna substrate 130 and the top section 131 disposed on the antenna substrate 130, and a space that laterally houses the amplifier substrate 134 are formed. The metallic antenna base 120 is fitted on a lower surface of the antenna case 110. The antenna substrate 130 is installed upright and fixed on the antenna base 120. The amplifier substrate 134 is fixed substantially parallel to the antenna base 120 in front of the antenna substrate 130. An antenna pattern is formed in an upper section of the antenna substrate 130. The top section 131 is built in an upper section of the antenna case 110. The antenna case 110 is fitted on the antenna base 120, and the top section 131 that is built in the antenna case 110 is so disposed as to straddle an upper section of the antenna substrate 130. A joint fitting 136 that is attached to an upper section of the antenna substrate 130 electrically comes in contact with an inner surface of the top section 131. The joint fitting 136 is electrically connected to the antenna pattern formed on the antenna substrate 130. Therefore, via the joint fitting 136, the top section 131 and the antenna pattern are connected. As a result, the antenna pattern and the top section 131 make up an antenna element; in a space inside the antenna case 110, the antenna substrate 130, the top section 131, and the amplifier substrate 134 are housed.
What is provided is a coil 135 that makes the antenna element which includes the antenna pattern and the top section 131 resonate around a FM wave band on the antenna substrate 130. One end of the coil 135 is connected to the antenna pattern. The other end of the coil 135 is connected to one end of a pattern formed on the antenna substrate 130. One end of a connection line 133 is connected to the other end of the pattern. The other end of the connection line 133 is connected to an input section of an AM/FM amplifier which is provided on the amplifier substrate 134. An AM/FM reception signal that is received by the antenna element including the antenna pattern and the top section 131 is input into the AM/FM amplifier and amplified. A bolt section 121 which is used to attach the antenna device 100 to the vehicle is so formed as to protrude from a lower surface of the antenna base 120. A cable 122 which feeds the reception signal from the antenna device 100 into the vehicle is extended out from a lower surface of the antenna base 120. The cable 122 is extended out from the amplifier substrate 134, and includes a cable that feeds an AM reception signal and FM reception signal that are amplified by the AM/FM amplifier provided on the amplifier substrate 134. Cables are bundled together by a collar 145. In this case, holes into which the bolt section 121 and the cable 122 are inserted are made in the roof of the vehicle. The antenna device 100 is placed on the roof in such a way that the bolt section 121 and the cable 122 are inserted into the holes. Then, a nut is fastened on the bolt section 121 that protrudes into the vehicle. As a result, the antenna device 100 is fixed to the roof of the vehicle. As for a power source for the amplifier substrate 134 that is housed in the antenna case 110, power is supplied to the amplifier substrate 134 from inside the vehicle via the cable 122.
The way the conventional antenna device 100 is assembled will be described with reference to an exploded view shown in FIG. 43. In the conventional antenna device 100, the top section 131 is fixed with two screws 140 to an upper section inside the antenna case 110. A joint fitting 136 is fitted on an upper end of the antenna substrate 130. The joint fitting 136 holds the antenna substrate 130. Therefore, the joint fitting 136 is attached to an upper section of the antenna substrate 130. The coil 135 is soldered onto the antenna substrate 130. The antenna substrate 130 is installed upright and fixed on the antenna base 120 with two screws 141. The amplifier substrate 134 is placed ahead of the antenna substrate 130, and is fixed with three screws 142 so as to be substantially parallel to the antenna base 120. The cable 122 which outputs the amplified AM and FM reception signals is extended out from the amplifier substrate 134. A terminal 143 is mounted on a tip of the cable 122. The terminal 143 is fixed to a back surface of the amplifier substrate 134. One end of the wire-like connection line 133 is connected to the antenna substrate 130. The other end of the connection line 133 is connected to the amplifier substrate 134. As a result, an output end of the coil 135 provided on the antenna substrate 130, and an input end of the AM/FM amplifier provided on the amplifier substrate 134 are connected; an AM/FM reception signal that is received by the antenna element including the antenna pattern and the top section 131 is input into the AM/FM amplifier on the amplifier substrate 134. The collar 145 is fitted to a base of the cable 122 in such a way as to bundle together the cable 122 that is pulled out from a pull-out hole of the antenna base 120.
A hook 144 is disposed, and is fitted on the antenna base 120 below the amplifier substrate 134. A pair of long engagement leg sections extend from both sides of the hook 144. When the antenna device 100 is attached to the vehicle, the engagement leg sections engage with an edge of a mounting hole that is formed on the vehicle, thereby working to temporarily fix the antenna device 100 to the vehicle body. Therefore, without holding the antenna device 100 from outside the vehicle body, it is possible to prevent the antenna device 100 from coming off the mounting hole when screwing the nut 147 on the bolt section 121 from inside the vehicle.
A base pad 124 is fitted on a lower surface of the antenna base 120. Five hole sections in total, into which heads of screws can be inserted are formed in a peripheral section of the base pad 124. Five screws 146 are inserted from below the hole sections. The screws 146 are inserted into fitting holes which are formed in a peripheral section of the antenna base 120, and are screwed into the periphery of the lower surface of the antenna case 110. In this manner, the antenna device 100 is assembled. The assembled antenna device 100 is attached in such a way that the bolt section 121 is aligned with the mounting hole that is formed on the vehicle. As a result, as described above, because of the hook 144, the antenna device 100 is temporarily fixed to the mounting hole. In this state, the nut 147 is screwed on the bolt section 121 from inside the vehicle. As a result, the antenna device 100 is attached to the vehicle body.
FIGS. 44 and 45 show the configuration of the antenna case 110 of the conventional antenna device 100. FIG. 44 is a side view showing the configuration of the antenna case 110 in cross section. FIG. 45 is a bottom view showing the configuration of the antenna case 110.
As shown in the diagrams, the antenna case 110 is made of synthetic resin that allows radio waves to pass therethrough, and has a streamline outer shape in such a way as to taper toward a tip. A space that houses the upright installed antenna substrate 130 and the top section 131 disposed on the antenna substrate 130, and a space that laterally houses the amplifier substrate 134 are formed in the antenna case 110. In order to put five screws, five screw holes 110c in total are formed on a lower surface: one in a front section, one in each of both sides of a central section, and one in each of both sides of a rear section. In order to form the screw holes 110c, five bosses 110b which bulge from around the screw holes 110c, are formed. Furthermore, two bosses 110e are formed in an upper section inside the antenna case 110 to fix the top section 131 with two screws 140.
As shown in FIGS. 42 and 43, the top section 131 of the conventional antenna device 100 is formed by processing a metal plate. The top section 131 includes an apex section with a curved surface that gradually goes down toward the front. A first side section and a second side section are so formed as to be inclined to both sides from the apex section. Three slits are formed on the first side section, and three slits on the second side section. Each of the side sections includes four pieces. Among the pieces, a pair of pieces that are almost near the center functions as contact pieces that are connected to the joint fitting 136. The middle portions of the contact pieces are bent and formed so as to be substantially vertical in such a way as not to come in contact with the bosses 110b which are so formed as to bulge toward the inside. Two flat sections are formed on the apex section of the top section 131. A screw hole is formed on each of the flat sections. Screws 140 are inserted into the screw holes, and screwed into the bosses 110e which are formed on an inner side of the apex section of the antenna case 110. Therefore, the top section 131 is attached inside the antenna case 110.
FIGS. 46 and 47 show the configuration of the antenna base 120 of the conventional antenna device 100. FIG. 46 is a plane view showing the configuration of the antenna base 120. FIG. 47 is a side view showing the configuration of the antenna base 120.
The antenna base 120 shown in the above diagrams is made of metal, and includes a main body section 120a that is substantially a rectangular plate that front section is tapered. Five fitting holes 120f are formed in total in a peripheral section of the main body section 120a. Screws 146 are inserted into the fitting holes 120f from below the fitting holes 120f, and are screwed into screw holes 110c which are formed on the lower surface of the antenna case 110. As a result, the antenna base 120 is fitted into the antenna case 110. Three bosses 120e are formed on the tapered front section of the main body section 120a. The amplifier substrate 134 is placed on the bosses 120e; screws 142 are inserted into the amplifier substrate 134, and are screwed into the bosses 120e. In this manner, the amplifier substrate 134 is fixed onto the antenna base 120.
Two screw sections 120d are formed in a horizontal direction in almost a central section and rear side of the main body section 120a. Screws 141 that are inserted into the mounting holes of the antenna substrate 130 are screwed into the screw sections 120d. As a result, the antenna substrate 130 is installed upright and attached to the antenna base 120. A rectangular-frame GPS antenna mounting section 120b which has a rectangular concave section is formed on a side that is slightly closer to a rear section of the main body section 120a than the center thereof. Screw holes 120c are formed at the four corners of the GPS antenna mounting section 120b. Four screws that are inserted into mounting holes of GPS antenna 132 are screwed into the screw holes 120c. In this manner, the GPS antenna 132 is mounted on the GPS antenna mounting section 120b. A rectangular cable pull-out hole 120h is formed in a central section of the main body section 120a. The cable 122 that is connected to the amplifier substrate 134 through the cable pull-out hole 120h, and a cable that is connected to the GPS antenna 132 can be pulled out.
Four first rectangular holes 120g and two second rectangular holes 120i are formed on a side that is slightly closer to a front section of the main body section 120a than the center thereof. Four fitting leg sections 144b of the hook 144 are inserted into the first rectangular holes 120g; the tips of the fitting leg sections 144b engage with a back surface of the antenna base 120. In this manner, the hook 144 is attached to the antenna base 120. Two engagement leg sections 144c of the hook 144 are inserted into the second rectangular holes 120i; the engagement leg sections 144b protrude from the lower surface of the antenna base 120 along the bolt section 121 as a result. The bolt section 121 is so formed as to protrude from a back surface of the main body section 120a. The collar 145 is provided to bundle together the cable 122 that is pulled out through the cable pull-out hole 120h. 
FIGS. 48 and 49 show the configuration of the base pad 124 of the conventional antenna device 100. FIG. 48 is a plane view showing the configuration of the base pad 124. FIG. 49 is a side view showing the configuration of the base pad 124.
The base pad 124 shown in the above diagrams is made of rubber or elastomer. The base pad 124 includes a main body section 124a that is a flat plate having the shape of a half-cut, elongated oval which has a curved surface that is tapered toward a front section, and that rear end is linear. A peripheral wall section 124b is formed and shaped in such a way as to goes along an outer shape of the antenna base 120 on a surface of the main body section 124a. The antenna base 120 is placed on a surface of the base pad 124, and the antenna base 120 is fitted into the peripheral wall section 124b. As a result, the base pad 124 is fitted on the antenna base 120. Five hole sections 124d are formed in total along an inner side of the peripheral wall section 124b. The heads of the screws 146 that are inserted into the fitting holes 120f of the antenna base 120 from below the fitting holes 120f are inserted into the hole sections 124d. An oval cut-out hole 124c is formed from the center of the main body section 124a to a front section thereof. The bolt section 121, cable 122, and collar 145, which are provided on the lower surface of the antenna base 120, protrude through the cut-out hole 124c. 